The invention relates to a device for frothing and steaming milk as well as to methods for frothing and steaming milk.
Such devices find application especially or together with espresso coffee machines. The milk froth created by the device is used for example in producing a cappuccino or latte whilst the steamed milk may be used both in preparing milk coffee as well as hot milk beverages.
Known devices usually feature a pivotably mounted steamer tube ending in a nozzle for jetting the steam. Jetting is started and stopped by means of a rotary switch or the like. To heat the milk the steamer tube is usually inerted relatively deeply into the receptacle containing the milk and the steam feed initiated. The steaming action is terminated as judged by the operator, the barista. To froth the milk the steamer tube is inserted into the milk just enough so that the jet of steam can entrain ambient air which ultimately is responsible for the frothing. Thus, how good the resulting milk froth is, depends on the expertise of the barista. When creating milk froth too, frothing is terminated as judged by the barista.
In addition to these simple devices fully automatic emulsifier units are known in which a steam feed conduit connected to the steamer ports into a suction chamber. This suction chamber is connected to a milk feed conduit and an air feed conduit. The flow of steam creates a negative pressure in the suction chamber causing the milk to be drawn into the suction chamber via the milk feed conduit and air via the air feed conduit. This steam/air/milk mixture is transformed into a turbulent flow in a subsequent emulsifier chamber, resulting in a hot emulsion of milk and air. One such emulsifier unit is known for example from EP-A-0 195 750.
However, fully automatic emulsifiers are relatively complicated and thus expensive to manufacture. On top of this, they tend to become soiled, making frequent cleaning a nuisance because the components coming into contact with the milk are not readily accessible from without and thus cannot be cleaned by hand. Apart from this, the milk has to be held in a separate, preferably chilled compartment or receptacle.
Disclosed in German patent DE 602 15 058 T2 is a device for steaming and frothing milk. The device comprises a calorifier connected via a first pipe—the steam pipe—to a delivery pipe. Inerted in addition in the steam pipe is a shutoff valve. The delivery pipe has an open end for immersing in a receptacle containing milk. the device comprises furthermore an electrically powered pump for feeding the air pressurized. The pump is connected via a second pipe to the delivery pipe. In conclusion, a temperature sensor is provided connected to the immersible end of the delivery pipe to serve sensing the temperature of the milk. In an alternative aspect the steam pipe is additionally provided with a bypass pipe to bypass the shutoff valve.